21668373 has 6 divisors (see below), whose sum is σ = 31298774. Its totient is φ = 14445576.

The previous prime is 21668327. The next prime is 21668389. The reversal of 21668373 is 37386612.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 20088324 + 1580049 = 4482^2 + 1257^2 .

It is not a de Polignac number, because 21668373 - 2⁹ = 21667861 is a prime.

It is a super-3 number, since 3×21668373³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663373) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1203790 + ... + 1203807.

Almost surely, 2^21668373 is an apocalyptic number.

It is an amenable number.

21668373 is a deficient number, since it is larger than the sum of its proper divisors (9630401).

21668373 is a wasteful number, since it uses less digits than its factorization.

21668373 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2407603 (or 2407600 counting only the distinct ones).

The product of its digits is 36288, while the sum is 36.

The square root of 21668373 is about 4654.9299672498. The cubic root of 21668373 is about 278.7888717601.

The spelling of 21668373 in words is "twenty-one million, six hundred sixty-eight thousand, three hundred seventy-three".